Pawl and ratchet mechanism



March 1,1960 F. o. WATSON PAWL AND RATCHET MECHANISM Filed June 4, 1957 F 1 G 1.

FIG-1.3.

INVENTOR FRANK O. WATSON ATTORNEY United States Patent ce 2,926,547

PAWL AND RATCHET MECHANISM Frank 0. Watson, Baltimore, Md., assignor to Bendix Aviation Corporation, Baltimore, Md., a corporation of Delaware Application June 4, 1957, Serial No. 663,498 4 Claims. (Cl. 74-575) An object of the present invention is to provide pawl and ratchet mechanism which is remarkably simple in construction, is compact and light in weight and hence adapted for restricted space installation, and at the same time is capable of performing with equal facility the functions of more complicated and expensive types of pawl and ratchet mechanism.

Another object is to provide pawl and ratchet mechanism in which a single pawl member or actuator may be used to impart rotation to a ratchet wheel or the like in either direction, the said pawl member being of onepiece construction and being capable of advancing the wheel and also locking the wheel in its advanced position.

A further object is to provide pawl and ratchet mechanism which requires a minimum of power to operate.

The foregoing and other objects and advantages will become apparent in view of the following description taken in conjunction with the drawing, wherein:

Figure 1 is a view in front elevation of a segment of a ratchet wheel and coacting paw] and ratchet mechanism in accordance with the invention;

Figure 2 is a side elevation of Figure 1 as indicated at 2-2; and

Figure 3 is a detail perspective view of the pawl member or actuator.

Referring to the drawing in detail, a ratchet wheel is mounted for rotation on a shaft 11. This wheel could be any type of rotatable element to which it may be desired to impart a step by step movement; it is formed with a plurality of ratchet teeth 12. In the present instance, the wheel 10 imparts a step movement to a code wheel 10', shown in Fig. 2 only. It is sometimes necessary to drive such wheels in either direction and to be able to stop the wheel in any selected angular position; also to rotate the wheel in increments of a tooth or multiple of teeth for each step.

Located adjacent the periphery of the wheel 10 is a pawl member or actuator 13; it consists of a flat piece of spring steel or other suitable spring material such as that used in small leaf springs, the strip of spring material being shaped in the form of a shallow U, thus providing two divergent legs or clicks 13 and 13", one of which serves as an advancing leg and the other as an overshoot locking leg, depending upon the direction of rotation it is desired to impart to the ratchet wheel. This pawl member or actuator is rockably connected to an actuator plate 14. Such rockable connection may be had by any convenient arrangement; in the present instance it is provided by a pair of loose rivets or headed pins 15, which project through holes formed in the spring metal at the base of the U, leaving sufiicient clearance between the inner heads and the plate 14 to permit of a limited rocking motion.

The pawl 13 may be driven in any suitable manner. In the present instance the drive mechanism comprises an electrical relay, generally indicated at 16, provided with an armature 17, which when the relay solenoid winding Patented Mar. 1, 1960 is energized is drawn towards solenoid pole piece or core 16' against the tension of a return spring 18. Since the plate 14 which carries the pawl 13 is connected to said armature, the pawl will be alternately pulled toward and away from the toothed periphery of the ratchet wheel 10. An arm 19 is connected at its one end to the plate 14 and a return stop 20 coacts with the opposite end of the arm to determine the exact position of the pawl with respect to the teeth of the ratchet wheel 10 when the pawl is rrtracted. Another spring 21 is connected to the one leg of the actuator and normally biases the latter to a position which will cause the advancing leg 13 to engage the teeth of the wheel 10 and advance the wheel the desired distance before the overshoot locking leg 13" holds the wheel against further advance rotation.

An adjusting screw 22 determines the biased or cocked position of the actuator when in its retracted position, and such position in turn determines the angular distance or number of teeth through which the ratchet wheel travels for each stroke of the relay armature.

A detent spring 23 may be provided to hold the ratchet wheel 10 stable when the actuators or pawl members 13 are idle or are both clear of the teeth of the ratchet wheel.

Operation In the example illustrated in the drawing, there are two actuators or pawl members working on a single ratchet wheel, the pawl members acting alternately to advance the wheel in opposite directions, or, in effect, selectively reverse the wheel and reposition the code wheel 10 in response to some parameter or parameters, such as changes in temperature and pressure of the atmosphere. The code wheel 10 has a commutating surface which, in connection with suitable electronic circuitry, generates electrical signals or intelligence to be received by a ground station. Each time one of the relays 16 is energized, it pulls its coacting annature plate 14 inwardly towards the teeth of the ratchet wheel, and this causes the leg 13' of the actuator or pawl member 13 to engage the teeth of the ratchet wheel and advance the latter through a given angular distance, which for example may correspond to two teeth of the ratchet wheel. When the wheel has been rotated through such distance, the leg 13" will also have engaged the ratchet wheel and the stroke of the relay will have been completed, the wheel then being momentarily locked against rotation in either direction until the relay is deenergized and the actuator pulled back or retracted by the spring 18. The relays are arranged in coacting pairs so that when one becomes energized the actuator or pawl member of the other will have been withdrawn from the teeth of the ratchet wheel, thereby permitting the wheel to be advanced or rotated in the opposite direction.

Simply by adjusting the screw 22 the distance through which the ratchet wheel is actuated for each stroke of the relay may be easily determined.

The actuator or pawl member 13 is of very low cost and easy to manufacture and install. Even so, it operates effectively, is quiet, and serves both as an advancing and locking element. Also, the actuators can be used interchangeably, or a single actuator cain serve to advance a ratchet wheel in either direction simply by reversing the spring connection 21 or by reversing the position of the actuator itself.

What is claimed is:

1. Pawl and ratchet mechanism including in combination with a rotatable radially-toothed ratchet wheel, a pawl member or actuator in the form of a strip of fiat spring material having a generally U-shaped contour thus providing a pair of substantially similar oppositelydiverging legs the free ends of which are adapted to abut end-on the trailing and leading faces of any two spaced-teeth of'said wheel, either of said legs being thus adapted to serve as an advancing leg for driving the wheel or as a trailing leg for positively locking the wheel against overshoot, meansfor biasing said pawl member in a-direction such that'one ofsaid'legs will engage a tooth of the ratchet wheel prior to'the other leg when the=said member is moved to wheel-actuating position, and a radially reciprocating support for said pawl member.

'2. Pawl and ratchet mechanism including in combination'with a rotatable radially-toothed ratchet wheel, a'pawl'member or actuator comprising a strip of'leaf spring material having a generally U-shaped contour with substantially similar 'oppositely-divergin legs the free 'ends of which are adapted to abut end-on the trailing and leading faces of any two spaced teeth of said wheel, either of said legs being thus adapted ,to

serveasian'advancing leg'fordriving the wheel or as a' trailing leg forpositively locking the wheel against over- "shoot, a radially=reciprocating support for said pawl member, means connecting the pawl member to its support permitting the pawl member to have limited rocking movement in the plane of the wheel, and means for biasing the advancing leg of said pawl member in a direction such that it will engage a tooth of the ratchet wheel prior to the trailing leg'when the pawl member is moved to Wheel-actuating position.

3. Pawl and ratchet mechanism including in combination with a'rotatable radially-toothed ratchet wheel, a pawl member or actuator in the form of a strip of leaf spring material having a generally U-shaped contour with oppositely-diverging legs of substantially the same length the free ends of which are adapted to abut end-0n the trailing and leading faces of any two spaced teeth of said wheel, means for supporting said member in a manner such 'asto permit it to have limited rocking movement in the plane of rotation of the wheel, means for radially reciprocating said supporting means, and means for biasing said pawl member in a direction such that the driving leg engages a tooth of the ratchet wheel prior to the trailing leg when'the actuator is moved to wheel-actuating position.

4. Pawl and ratchet mechanism including in combination with a rotatable radially-toothed ratchet wheel, va pawl member or actuator .comprisinga strip of leaf spring material having a generally U-shaped contour with substantially similar oppositely-diverging legs the free ends of which are adapted to abut end-0n the trailing and leading faces rof'any two spaced teeth of said wheel,

I either of said legs being thus adapted to serve as an advancing leg for driving the wheel or as a trailing leg for positively locking the wheel against overshoot, a support for said member, means connecting said member to sai'd support at the base pf, the ,U'in a manner such that said. member is permitted limited rocking movement in the plane of rotation of the wheel, means 'forradially reciprocating said support, a spring biasing said member in a direction such that the drivingilegs will engage-a tooth of the ratchet wheel prior to the trailing legwhen the said'member is moved to wheel-actuating position, and adjustable stop means for limiting the biasing position of said member when the'latter is disengaged'from said teeth.

References Qited in thefilesofxthis patent FOREIGN PATENTS 6109/32 Australia -,Oct..l2 .1932 112,183 Australia ...Jan. 24, 1940 721,753 Great Britain Jan. ,12, 195.5 

